Patterning Oxide Nanopillars at the Atomic Scale by Phase Transformation

Research News

Patterning Oxide Nanopillars at the Atomic Scale by Phase Transformation

2015-10-15

Researchers at Tohoku University's Advanced Institute for Materials Research (AIMR) have carried out a collaborative study aimed at precisely controlling phase transformations with high spatial precision, which represents a significant step forward in realizing new functionalities in confined dimensions.

The team, led by Prof. Yuichi Ikuhara, applied the focused electron beam of a scanning transmission electron microscope (STEM) to irradiate SrNbO3.4 crystals, and demonstrated a precise control of a phase transformation from layered SrNbO3.4 to perovskite SrNbO3 at the atomic scale.

Such a precise control of phase transformations opens up new avenues for materials design and processing, as well as advanced nanodevice fabrication. Full results of the study have been published in Nano Letters.

Background

Phase transformations in crystalline materials are of primary fundamental interest and practical significance in a wide range of fields, including materials science, information storage and geological science. To date, it remains highly desirable to precisely tailor the phase transformations in a material due to their potential impact on macroscopic properties and thus many advanced applications.

Despite decades of efforts, precisely controlling phase transformations at the atomic scale still poses a significant challenge due to the intricacies of governing thermodynamic conditions with atomic precision. Recent technical advances in aberration-corrected STEM offer fertile new ground for probing samples by a focused sub-Angström electron beam, opening an avenue for precisely triggering phase transformations.

Breakthrough

This work has demonstrated a successful control of a phase transformation from the layered SrNbO3.4 to the perovskite SrNbO3 with atomic precision by manipulating a focused sub-Angström electron beam to any selectable region.

Such a concept - of a precise control of phase transformations with an atomic spatial precision - should be, in principle, applicable not only to SrNbO3.4/SrNbO3 but also to other materials, finding applications in material processing and nanodevice fabrication.

(Figure 1.) Atomic zip in SrNbO3.4. (a) HAADF STEM image taken before irradiation. The irradiation area is marked by a red open rectangle. (b) HAADF STEM image taken after the electron irradiation for ~300 s showing changes in atomic structure in the irradiated region. The zigzag-like slab in the rectangle is transformed to a chain-like connected structure, resulting in atomic merging of the two neighboring chain-like slabs. The new phase has adopted the structure of SrNbO3. The phase transformation can be well controlled with atomic precision.